US2689115A - Carburetor - Google Patents

Description

Patented Sept. 14, 1954 CARBURETOR Elmer Olson, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application March 23, 1951, Serial No. 217,123

9 Claims.

This invention relates to carburetors for internal combustion engines, particularly for automotive use and more specifically to the means for supplying combustible mixture to the engine during idling and near or off idling operation.

The primary object of the present invention is to provide means for supplying fuel mixture for idling or near idling operation which is eifective to supply a mixture having substantially a correct fuel-air ratio and will neither be too rich nor too lean in any part of the idle or near idle range. tion is embodied in a carburetor of the type shown in the copending application of Elmer Olson, Serial No. 109,347, filed August 9, 1949, but the invention is not designed to be applicable to this particular carburetor only.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred embodiment of the present invention is clearly shown.

In the drawings:

Fig. 1 is a vertical section through the carburetor in which the present invention is embodied.

Fig. 2 is a detail section on the line 22 of Fig. 1.

Fig. 3 is a similar detail section showing a modified form of the invention.

Referring to Fig. 1, the carburetor shown therein comprises three separate castings numbered I, 2 and 3, respectively. The casting l is the carburetor outlet which is adapted to be connected with the intake manifold in the usual manner, the casting 2 is positioned above the outlet casting l and has a constant level fuel chamber 2a formed therein, while the casting 3 forms a cover for the fuel chamber and also has the air intake 4 formed therein. These three castings are separated by gaskets to form tight joints and to limit the transfer of heat between the castings as much as possible by preventing any metallic contact of the castings with each other.

In the outlet casting l, a throttle shaft 5 is suitably journalled and secured to such shaft is the usual throttle valve 6 which is manually adjustable by means not shown to control the volume of combustible mixture which is supplied by the carburetor to the engine.

In the casting 3 a choke valve 1 is positioned and this valve is secured to a shaft 8 which is suitably mounted in the casting 3 for rotation. The choke valve in the carburetor disclosed here- As illustrated herein, the present invenin is manually operated and, when the engine is operating at normal temperature, is adapted to be positioned in wide open position so as not to restrict the quantity of air entering the carburetor, but is adapted to beclosed, or partly closed, by the manual operating connections when the engine is started cold in order to facilitate starting, the position to which the choke valve is moved being dependent upon the temperature at the time of starting. The choke valve is adapted to be moved to different positions by means of the arm numbered 9 which is adapted to be operated by a connection leading to the dash which is not shown herein, but is of a conventional construction. The arm 9 operates the choke valve through mechanism which need not be described herein, but is fully shown and described in the copending application above referred to. It may be said, however, that the operation of the choke valve by the arm 9 is eifected through a spring I0 which holds the choke valve yieldingly closed, so that when the engine starts to run under its own power, the increase in engine suction which then occurs can pull the valve open to som extent against the force of the spring Ill, so as to prevent overchoking.

In the carburetor shown herein, the choke valve is also designed to operate the throttle so as to move the throttle slightly toward open position when the choke valve is moved to its fully closed position in order that the idling speed may be somewhat increased when the choke valve is closed. This is done for the purpose of providing a somewhat faster than normal idling when the choke valve is closed at low temperatures which is desirable to prevent stalling. The operating connections between the choke valve and the throttle valve. for efiecting this movement are indicated generally by the reference numeral ll. Since this mechanism has nothing to do with the invention in this application, it is not illustrated in detail and will not be described, but such mechanism is fully shown and described, in the aforesaid copending application.

As already indicated, air is admitted to the carburetor through the air inlet 4 and fuel is supplied to the carburetor through a main fuel nozzle I2 which terminates at the throat of a small Venturi tube [3, which itself, terminates at the throat of a large Venturi tube l4 integral with the casting 2 and forming a part of the mixture passage which extends vertically through the carburetor. The purpose of these Venturi tubes is, of course, to increase the velocity of air flow past the end of the main fuel nozzle 12 to create a partial vacuum adjacent the nozzle outlet in the usual and well known manner. Fuel is also supplied to the intake passage by an idling fuel inlet which is shown in Fig. 2 and in modified form in Fig. 3. The construction of these idling fuel inlets will be later described.

Fuel is supplied to the main and idling fuel inlets from the fuel chamber 2a and fuel is supplied to the latter through a coupling it which is screwed into the casting 3 and to which a fuel supply pipe extending to the main fuel tank of the vehicle is adapted to be connected. Fuel which is supplied through the coupling [:5 enters a passage I6 formed in the casting 3 and flows through a passage in a nipple 17, which is screwed in the wall of the casting 3, and communicates with the fuel bowl 2a when the parts are assembled as shown in Fig. l. The flow of fuel through the passage l1 into the bowl is controlled by a valve i8 which cooperates with the passage I1 and rests on one arm of a lever [9 which is pivoted on a pin fixed in position in the wall of the fuel chamber 2a. The lever I9 is connected to the float mechanism which is not shown, but which is received within the chamber 2a and when the fuel level in said chamber reaches a definite height, the float lifts the lever [B so as to close the valve I8 and cut oif the flow of fuel into the float chamber in the usual way. The float mechanism is of conventional construction and has nothing to do with the invention which is claimed in this application.

Before describing the fuel passage which conveys fuel from the float chamber 2a to the main and idling fuel inlets, attention is called to the fact that the carburetor is provided with an accelerator pump which is operated manually upon sudden opening movements of the throttle to provide a charge of fuel in addition to the fuel supplied by the ordinary fuel inlet, in order to enrich the mixture for acceleration in the usual way. The construction of this accelerator pump constitutes no part of the present invention, but the pump includes a cylinder into which fuel flows from the float chamber 2a, through a passage, not shown, and slidable in the cylinder is a pump piston 26 which is operated by a spring 2'! that is compressed when the throttle is opened suddenly, by means of an arm 26a which is pulled downwardly when the throttle is opened. This compression of the spring effects a delayed downward movement of the piston 26 which takes place as the spring expands following its compression by the throttle, as the latter is opened and as the piston moves downwardly, in the manner described, it forces fuel from the space below the piston into the mixture passage to supply the additional fuel above referred to for acceleration purposes. This pump mechanism is fully shown and described in the copending application above referred to and will not be further described herein, since its construction is entirely immaterial so far as the present invention is concerned. A tube 28 which connects the upper end of the cylinder '25 with the carburetor intake serves as a vent for escape of any fuel bubbles which may collect within the cylinder 25 and as a vent for the fuel chamber 2a.

The construction which has been generally described above is the same as that disclosed in Ser. No. 109,347 and the construction of the entire carburetor may be the same except the means for supplying idling and part throttle mixture which will be described in detail later. In this application as well as in the earlier application the fuel conduit leading to the main and idling fuel inlets comprises three parts or passages which together make up a conduit shaped substantially like an inverted U, one part or passage being substantially'vertical and extending downwardly into the float chamber and connecting at its upper end with a horizontal passage formed in casting 3, which, in turn, connects at its other end with a substantially vertical passage that extends downwardly to the idling fuel inlet, the main fuel inlet communicating with the horizontal portion of the passage substantially midway between its ends. As shown in Fig. 1, the fuel conduit includes a vertical passage 30 formed in a member 3| which, at its upper end, is secured in any suitable way in a bore or chamber 31a formed in the casting 3. This member, at its lower end, has a calibrated plug 32 screwed into it which meters the fuel supplied to passage 30. Communicating with the chamber am is a horizontal passage 33 which, at its left end, as shown in Fig. 1, connects with a vertical passage 34 which extends downwardly in the wall of the casting 2 and communicates at its lower end with a passage 35 which leads to the idling fuel inlet, which will be later described. The passage 35 is a channel formed in the bottom of the casting 2 and connects the passage 34 with a part of the idling fuel supply passage which is formed on the casting 4 and is positioned from passage 3d when the carburetor is assembled. The horizontal portion 33 of the fuel conduit is of different diameters, that part of the passage lying between the chamber 3m and the point of connection with the main nozzle being smaller than that part 36 of the passage 33 which lies to the left of the main nozzle in Fig. l. A plug 31 closes the left end of the passage and a tube 38 is fitted in that part of the fuel passage numbered 36. Such tube has a restricted opening 38a at its right end and terminates somewhat to the right of the vertical passage 34. A'plurality of orifices 39 are provided immediately above the main nozzle [2 to admit air for purposes of effecting atomization of the fuel and a bushing 40 having a small orifice 4| therein is positioned within the main nozzle [2 to cause a flow therethrough at high velocity and to aid in the atomization of the fuel. This fuel passage as so far described, is of the same'construction as that shown in the earlier application.

The fuel passage 33 delivers solid fuel to the space above the bushing 40 in which it ismixed with air entering the orifices 39 and the mixture thus formed is discharged into the mixture passage through the idling fuel supply passage, or the main nozzle I2 orboth, depending on the throttle position. When the throttle is closed for idling the suction at the idling fuel inlet, which connects with the mixture passage posterior to the throttle, is so great that there is no flow from the main nozzle. As the throttle is moved toward open position the suction at'the main nozzle is'increased while that at the idling fuel inlet is reduced, so that during a part of the throttle movement fuel is supplied by both inlets and as the throttle continues to move toward open position the idling fuel inlet ceases to function and all of the fuel is supplied by the main inlet.

According to the present invention the idling fuel supply passage 35 in the bottom" of casting 2 connects with a vertical bore 45 in the wall of the throttle body casting l which is located 90 circumferentially from the passage 34 as clearly shown in Fig. 2. The passage 45 connects at the lower end with a diagonal passage 45 which leads to a restricted inlet 41 connected with the mixture passage. A manually adjustable valve 43 which is retained in any adjusted position by a spring 45 controls the inlet 41, while a plug having a passage 55 of small size therein is positioned in the passage 45 adjacent its point of connection with the passage 35. Formed in the wall of the throttle body casting I parallel to and adjacent the passage 45 is a bore 5| closed at its upper end by the bottom face of the casting 2. A small passage 52 connects this bore with passage 45, while two passages 53 and 54 connect bore 5! with the carburetor intake passage. As illustrated, the passage 54 is somewhat larger than the passages 52 and 53 and these are shown as of about the same size, but the drawings are not on exact scale, and the several passages are not shown in the drawings in their exact size. The passages are of such sizes that the desired mixture proportions will be obtained during the idle and near idle range of operation.

The operation of the passages above described is as set forth hereinafter. When the throttle valve is in the fully closed or idle position, as shown, both the passages 53 and 54 are on the anterior side of the throttle, while the inlet 4'! is posterior to the throttle. The high manifold vacuum is communicated to the opening 4'! and through this opening to the passage 45, but the effect of this high suction on the passage 45 is reduced by the action of the passages 52, 53 and 54 which permit air to flow from the mixture passage through passages 53 and 54 and thence into passage 45 through passage 52. Obviously, this admission of air reduces the suction created in passage 45 and the effect of such suction on the flow of fuel is still further reduced by the effect of the restricted opening 50. By setting the valve 48 in proper position, an idling mixture of proper proportions is obtained.

As the throttle is moved slightly toward open position for near or off idle operation, the passage 53 ceases to function as a bleed, such passage becoming subject to the high suction maintained posterior to the throttle and acting to supply fuel mixture to the intake passage. When this takesplace, fuel is being supplied through both the passages M and 53 and the passage 53 has also become a suction passage instead of a bleed. This action tends to cause the off idle mixture to become too rich, but this is prevented by the action of the orifice 5 1 which continues to act as a bleed and breaks the effect of suction on passages 47 and 53 sufiiciently to prevent the off idle mixture becoming too rich after the passage 53 has become a fuel supply passage.

As the throttle progressively opens, the passages 4'1 and 53 continue to supply fuel mixture at a progressively decreasing rate due to the reduction of suction on such passages until the suction at the main nozzle becomes so great that there is a reverse flow through the passages 41 and 53 from the intake passage toward the main nozzle, after which all of the fuel is supplied by the main nozzle alone. Before this takes place, the main nozzle has begun to function for as already stated, during a part of the opening tie is closed to movement of the throttle there is a flow of fuel from the main nozzle as well as from the passages 41 and 53. The passage 54 is located so far above the throttle that it never acts as a fuel supply passage, but is always a bleed.

It will be understood that the effect of the bleed hole 54 is very slight at idling, in fact, substantially negligible because at idling the passage 53 is also a bleed and the passage 52 is of such small size that its efiect would be much the same if passage 54 were omitted, when the throtidling position. When the throttle begins to open, however, the bleeding action of the orifice 54 so modifies the efiect of suction, particularly on passage 55 that it is effective to prevent the mixture becoming too rich.

It is old to employ a small orifice 53 to connect the intake passage with a passage such as 45, in fact, such an arrangement is shown in the application previously referred to. With this arrangement a correct idling mixture can be obtained with proper adjustment of the valve 48, but when the throttle is slightly opened for 01f idle operation, the mixture tends to become too rich. If a restriction such as 55 is put in the passage 45, and the orifice 53 omitted, a correct idling mixture would be still obtainable by proper adjustment of the valve 48, but the off idling mixture would become considerably too lean. If a small orifice 53 is used with a restriction such as 59, for the purpose of correcting the leanness referred to, even if the orifice is as small as it is practical to use, the oif idle mixture tends to become too rich. By employing a bleed hole 54 of proper size, to modify the effect of suction on the orifice 53, the tendency to over-richness at oif idle operation can be averted without making the mixture too lean in any part of the idle and near idle range.

While the construction and operation of a device employing the restriction 55 in addition to the orifices 54, as a means for modifying the mixture proportions at off idle operation, has been described and such construction is probably preferable for some reasons, the restriction 55 can be omitted and if the sizes of the various orifices have the proper relation, the mixture proportions can be adequately controlled without employing a restriction in the passage 45. In other words, if the orifice sizes are properly selected, a satisfactory result can be obtained without use of the restriction 55.

The construction shown in Fig. 3 is of slightly different form but functions in the same way as does that previously described. In this form of the device a chamber 55 is formed in the Wall of the throttle body casting l and a plug is positioned therein having a flange 5| of the same diameter as the chamber and a reduced cylindrical extension 62, between the outer wall of which and the Wall of the chamber is an annular space 53. A restricted opening 55a corresponding to the opening 53 connects the passage 35 with the interior of the extension 52 and passages 53a and 54a, corresponding to passages 53 and 54 connect the space 53 with the intake passage, while a passage 52a connects the space 53 with the interior of extension 62. The operation of this modified form of the device is just the same as that shown in Fig. 2 and need not be specifically described.

While the embodiment of the present invention as herein disclosed constitutes a preferred form,.it is to be understood that other forms might be adopted.

-What is claimed is as follows:

I. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling. fuel supply passage operable to supply fuel tothe intake passage when the throttle is open to less than a predetermined extent, a fuel conduit for conveying fuel from the fuel supply chamber to said main fuel inlet and to said idling fuel supply passage, a passage connecting the idling fuel supply passage with the intake passage ata point posterior to the throttle valve in all positions, a second fuel passage having a relatively' small opening connecting it with the idling fuel passage, and a plurality of passages connecting said second fuel passage with said intake at points anterior to the throttle valve when the latter is in closed position, said last-named passages being so positioned with respect to the throttle valve that they progressively become posterior to the throttle valve when said valve is moved to predetermined open positions and one of'which supplies fuel to said intake passage.

2.- A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling fuel supply passage operable to supply fuel tothe intake passage when the throttle is open to less than a predetermined extent, a fuel conduit for conveying fuel from the fuel supply chamber to said main fuel inlet and to said idling fuel supply passage, a passage connecting the idling fuel'supply passage with the intake passage at a point posterior to the throttle valve in all positions, a second fuel passage having a relatively small opening connecting it with the idling fuel passage, a plurality of passages connecting said second fuel passage with said intake at points anterior to the throttle valve when the latter is in closed position, said last-named passages being so positioned with respect to the throttle valve that they progressively become posterior to the throttle valve when said valve is moved to predetermined open positions, and a restriction in said idling fuel supply passage anterior to the point of connection of any of the aforementioned passages therewith, one of said plurality of passages being effective to supply fuel upon a predetermined movement of the throttle.

3. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of com bustible mixture therethrough, a main fuelinlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, a fuel conduit for conveyii' fuel. from the fuel supply chamber to the main fuel inlet, an idling fuel supply passage operable to supply fuel to the intake when the throttle is open to less than a predetermined extent and connecting with said fuel conduit at a point closely adjacent to the main fuel inlet, a passage connecting the idling fuel supply passage with the intake passage at a point posterior to the throttle valve in all positions, and a plurality of passages connecting said idling fuel supply passage with said intake at points anterior to the throttle valve when the latter is in closed position, said passages being so positioned with respect to the throttle valve that they progressively become posterior to the throttle valve when said valve is moved to predetermined open positions, but one of said passages serving as a vent only in all positions of the throttle valve.

4. A carburetor for internal combustion engines, having in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, a fuel conduit for conveying fuel from the fuel supply chamber to the main fuel inlet, an idling fuel supply passage operable to supply fuel to the intake passage when the throttle is open to less than a predetermined extent and connecting with said fuel conduit at a point closely adjacent to the main fuel inlet, a passage connecting the idling fuel supply passage with the intake passage at a point posterior to the throttle valve in all positions, a second fuel supply passage connected with the first idling fuel supply passage by a connecting passage of small size operable to limit the rate of fuel flow to said second fuel supply passage and a plurality of passages of larger size than said connecting passage for connecting the second fuel supply passage with the mixture passage, at points anterior to the throttle valve when the latter is in closed position, said last-named passages being so positioned with respect to the throttle valve that they are progressively rendered subject to the suction maintained posterior to the throttle valve as said valve is moved toward open position.

5. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, a fuel conduit for conveying fuel from the fuel supply chamber to the main fuel inlet, an idling fuel supply passage operable to supply fuel to the intake passage when the throttle is open to less than a predetermined extent and connecting with said fuel conduit at a point closely adjacent to the main fuel inlet, means for admitting air to said idling fuel supply passage at its point of connection with said fuel conduit to form therein a mixture of fuel and air, a passage connecting the idling fuel supply passage with the .take passage at a point posterior to the throttle in all positions, a second fuel supply passage connected with the first idling fuel supply passage by a connecting passage of small size operable to limit the rate of fuel flow to said second fuel supply passage and a plurality of passages of different sizes connecting said second fuel supply passage with the intake passage at a point anterior to the throttle when the latter is closed, all of said last-named connecting passages being of larger size than the first connecting passage, said passages being so positioned with respect to the throttle valve that they are progressively rendered subject to the suction maintained posterior to the throttle valve as said valve is moved toward open position.

6. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling fuel supply passage through which fuel flows when the throttle is closed or open to less than a predetermined degree, a chamber, a flanged cylindrical element in said chamber forming an annular space between itself and the chamber wall, said cylindrical element communicating with the idling fuel supply passage, a passage connecting the interior of said cylindrical element with the intake passage at a point posterior to the throttle valve, a plurality of passages connecting said annular space with the intake passage at points anterior to the throttle valve when the latter is in closed position and so positioned with respect to the throttle valve that they progressively become posterior to said throttle valve when it is moved to predetermined open positions, and a passage connecting said annular space with the interior of said cylindrical element.

7. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling fuel supply passage through which fuel flows when the throttle is closed or open to less than a predetermined degree, a chamber, a flanged cylindrical element in said chamber forming an annular space between itself and the chamber wall, said cylindrical element communicating with the idling fuel supply passage, a passage connecting the interior of said cylindrical element with the intake passage at a point posterior to the throttle valve, a plurality of passages connecting said annular space with the intake passage at points anterior to the throttle valve when the latter is in closed position and so positioned with respect to the throttle valve that they progressively become posterior to said throttle valve when it is moved to predetermined open positions, a passage connecting said annular space with the interior of said cylindrical element and a restricted opening connecting the idling fuel supply passage with said cylindrical element.

8. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling fuel supply passage operable to supply fuel to the intake passage when the throttle is open to less than a predetermined extent, a fuel concluit for conveying fuel from the fuel supply chamber to said main fuel inlet and to said idling fuel supply passage, a passage connecting the idling fuel supply passage with the intake passage at a point posterior to the throttle valve in all positions, an additional fuel passage substantially parallel to said idling fuel supply passage and connected therewith through a restricted orilice which controls the rate of fuel flow into said additional passage, a restriction in said idling fuel supply passage anterior to and adjacent said restricted orifice, and a plurality of passages connecting said additional fuel passage and the intake passage anterior to the throttle when in closed position, said plurality of passages being so positioned with respect to the throttle valve that they progressively become posterior to the throttle valve when the throttle valve is moved to predetermined open positions.

9. A carburetor for internal combustion engines having, in combination, a constant level fuel supply chamber, an intake passage provided with a throttle valve for controlling the flow of combustible mixture therethrough, a main fuel inlet for supplying fuel to the intake passage after the throttle is opened to a predetermined extent, an idling fuel supply passage operable to supply fuel to the intake passage when the throttle is open to less than a predetermined extent, a fuel conduit for conveying fuel from the fuel supply chamber to said main fuel inlet and to said idling fuel supply passage, a passage connecting the idling fuel supply passage with the intake passage at a point posterior to the throttle valve in all positions, an additional fuel passage substantially parallel to said idling fuel supply passage and connected therewith through a restricted orifice, and a plurality of passages of larger size than said restricted orifice connecting said additional fuel passage and the intake passage anterior to said throttle valve when in closed position, said plurality of passages being so positioned with respect to the throttle valve that they progressively become posterior to the throttle valve as the throttle valve is moved to predetermined open positions.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,895,471 Mathieu Jan. 31, 1933 2,009,280 S'prenger July 23, 1935 2,035,681 Udale Mar. 31, 1936 2,987,293 Olson July 20, 1937 2,127,444 Emerson Aug. 16, 1938 2,215,683 Wirth Sept. 24, 1940

Images